1. Field of the Invention
The present invention relates to stimulation of collateral development in ischemic cardiac regions, more specifically to a method and apparatus for coupling left ventricle of the heart to the anterior interventricular vein to stimulate collateral development in ischemic regions.
2. Background Information
Heart disease is the leading cause of death for both men and women. According to the Center for Disease Control and Prevention, every year, about 720,000 Americans have a heart attack. Approximately 600,000 people die from cardiovascular disease (CVD) in the United States each year (about 1 out of every 4 deaths) with an estimated cost of health care services, medication, and lost productivity from cardiovascular disease at approximately $312 Billion.
A lack of oxygenated blood to the myocardial tissue creates ischemia and is the most common condition presented in the clinic requiring treatment for heart disease. Currently, there are three treatments for CVD: 1) lifestyle change, 2) medications (optimal medical therapy) and 3) Interventional procedures and devices such as angioplasty and stenting, coronary artery bypass (CABG), and circulatory support devices.
The focus of interventional treatments has been on epicardial coronary arteries as a means to reestablish flow to ischemic tissue; the two most common procedures are percutaneous transluminal coronary angioplasty (PTCA), and CABG. These procedures can be limited by a number of complications such as abrupt vessel closure, restenosis, lesions that are totally occluded, and diffuse or long lesions that may not be “stentable.”
Perhaps most significantly, occlusion of a coronary artery can cause detrimental changes to occur in the cardiac arterioles and capillaries that cause the so-called “no-reflow phenomenon” post CABG or PTCA. “No-reflow” may prevent adequate healing of ischemic tissue and inhibit development of collateral vasculature. Additionally, no-reflow is more pronounced in the sub-endocardium and becomes more common the longer the myocardium remains ischemic. Other anatomical anomalies, porcelain vessels, and lack of useful grafting tissue compound a myriad of problems that complicate “normal” coronary disease treatments.
An estimated 15% of the population presenting in the clinic are not suitable for CABG. For this so-called “no-option” patient population, mechanical circulatory support devices (VADs) or eventually heart transplant may be the only options.
It has long been proposed to deliver oxygenated arterial blood delivery through the coronary venous system 30, called retroperfusion, to the ischemic myocardium, with original proposals dating back to at least 1898, Pratt FH., The nutrition of the heart through the vessels of Thebesian and the coronary veins. Am J Physiol 1: 86-103,1898, proposed the idea of perfusion of the heart muscle through the coronary sinus in isolated feline hearts. This work suggested that venous retroperfusion can provide some degree of nutritional delivery. In 1949, Beck C. Revascularization of the heart. Surgery 26: 82-88, 1949 described initial attempts of chronic retroperfusion of the coronary sinus by means of anastomosis to an arterial vessel [coronary venous bypass graft, (CVBG)]. In 1956, Lillehei C W, DeWall R A, Gott V L, Varco R L., The direct vision correction of calcification of calcific aortic stenosis by means of pump-oxygenator and retrograde coronary sinus perfusion. Dis Chest 30: 123-132, 1956 was the first to use this technique during cardiac surgery for myocardial protection.
Coronary retroperfusion was quickly abandoned, however, because of structural damage of the coronary sinus wall as well as intramyocardial vasculature produced by drainage disruption and elevated pressures (see Syeda B, Schukro C, Heinze G, Modaressi K, Glogar D, Maurer G, Mohl W. The salvage potential of coronary sinus interventions: meta-analysis and pathophysiologic consequences. J Thorac Cardiovasc Surg 127: 1703-1712, 2004.) Hemorrhage of the myocardium was reported as a complication during retroperfusion involving an arteriovenous shunt driven by an external roller pump through a catheter wedged in the anterior interventricular vein (See Zalewski A, Goldberg S, Slysh S, Maroko P R. Myocardial protection via coronary sinus interventions: superior effects of arterialization compared with intermittent occlusion. Circulation 71: 1215-1223, 1985). These complications, in conjunction with the adoption of coronary artery bypass grafting (CABG) and the eventual development of percutaneous transluminal coronary angioplasty (PTCA), limited the retroperfusion concept and coronary sinus interventions clinically.
At least two distinct pumpless approaches of coronary retroperfusion have been described relatively recently, both with arguable potential for chronic application: 1) percutaneous in situ coronary venous arterialization (PICVA) and 2) stent-based ventricle-to-vein bypass (venous VPASS).
PICVA is a catheter-based technique developed to provide arterial blood flow from the native coronary artery to the coronary vein while the outflow toward the coronary sinus is blocked (See Oesterle S N, Reifart N, Hauptmann E, Hayase M, Yeung A C. Percutaneous in situ coronary venous arterialization. Report of the first human catheter-based coronary artery bypass. Circulation 103: 2539-2543, 2001.) The major limitation of this approach is the procedural complexity, requiring penetration of the arterial wall to access the nearby vein, which is often difficult in no-option patients with significant diffuse disease. Furthermore, this method creates a sudden increase in coronary venous pressure and may be associated with subsequent myocardial hemorrhage.
The earlier VPASS approaches have included catheter-based approaches, which placed a stent based device designed to provide systolic blood flow directly from the left ventricle into either a coronary artery or a coronary vein. One limitation of this procedure as proposed is the necessity of selective catheterization of the veins draining the ischemic territory (See Raake P, Hinkel1 R, Kupatt C, von Brühl ML, Beller S, Andrees M, Vicol C, Boekstegers P. Percutaneous approach to a stent-based ventricle to coronary vein bypass (venous VPASS): comparison to catheter-based selective pressure-regulated retro-infusion of the coronary vein. Eur Heart J 26: 1228-1234, 2005). A more fundamental limitation is the inability of this approach as developed is to provide complete perfusion of the subendocardium during systole. Furthermore, the blood may be suctioned from the coronary venous system during diastole.
Thus there remains a great need in the art for a method and associated system to re-establish flow of oxygenated blood to tissue that has been starved due to stenosis or occlusion from emboli and may be positioned as an alternative or adjunct to PTCA, CABG, or mechanical circulatory support (VADs).